Anti-theft system for a radio receiver used particularly in a motor vehicle

ABSTRACT

The present invention relates to a system for receiving radio-waves used in a motor vehicle. The system is characterized in that it comprises an amplification unit (3) presenting a housing (5) of a removable tuner control part (4) which, when introduced in the housing (5) is electrically connected to the amplification unit (3) in order to make the reception system operative. The present invention applies particularly to the protection against theft of car radios.

BACKGROUND OF THE INVENTION

The present invention relates to a thief-proof system for radioreceivers used in particular in an automotive vehicle.

Radio receivers mounted in particular in automotive vehicles are socoveted that a number of parked vehicles are broken into in order tosteal for example through pulling out, the radio receiver.

In order to dissuade people from stealing radio receivers, it hasalready been proposed to mount in a removable manner the radio receiveron the dashboard of the vehicle.

However, due to the bulkiness of the radio receiver, the owner of thevehicle when he leaves it parked for a limited duration, often hides theradio receiver inside his vehicle, for example under a front seatthereof. This behaviour is well known from the thieves, so that theyjust have to break a window of the vehicle and to take rapidly thehidden radio receiver.

SUMMARY OF THE INVENTION

The present invention provides a system dissuading any people fromcoveting a radio receiver mounted inside an automotive vehicle.

For this purpose, the system for receiving radio waves according to theinvention, used in particular in an automotive vehicle and of the typecomprising essentially an audio amplifying unit solid in an inviolablemanner with a stationary part of the vehicle such as the dashboard and apart for controlling the selection of the radio waves or tuner control,fastened in a removable manner to the amplifying unit and connected tothe same through the medium of electric connection means making thetuner control unit operational, is characterized in that the amplifyingunit comprises a housing for receiving the tuner control unit forelectrically connecting the same to the amplifying unit and in that thetuner control unit presents on its visible outer part, once received inthe housing, elements for controlling the search for radio wavesfrequencies and for selecting the waves and a device for displaying inparticular the search frequencies.

According to an advantageous feature of the invention, the tuner controlunit is in the shape of a flat right angled parallelepiped having a sizesimilar to that of a credit card.

Thus, before leaving his vehicle, the user simply removes the tunercontrol from the amplifying unit so that the later be practically hiddenand, due to the low bulkiness of the tuner control unit, the user cancarry it away for example in his pocket.

Preferably, the amplifying unit is fastened behind the dashboard of thevehicle which comprises an aperture in front of the inlet of the housingof the amplifying unit for the passage of the tuner control.

The aforesaid electrical connecting means are formed of plugging meanscomprising a connector received in the lower part of the housing of theamplifying unit and comprising a certain number of resilient metallicstrips cooperating respectively with metallic contacts which are solidwith the tuner control unit.

It may be desirable not to effect the connection of the tuner controlunit to the amplifying unit through the medium of the metallicstrip-electrical contact assembly for reasons or reliability. Indeed,the extraction and the insertion of the tuner control unit from and intothe amplifying unit can occur often during the day, so that a rapidwearing of the contacts is likely to occur. Moreover, these contacts maydeteriorate due to the presence of metallic articles, such as a keyand/or a coin during the transport of the tuner control unit inside apocket.

To solve these problems, the system according to the invention providesalso means for connecting the tuner control unit to the amplifying unitcomprising a capacitive coupling-type connection for the transmission ofhigh frequency signals coming from the antenna to the high frequencycircuits of the tuner control unit, a capacitive coupling-typeconnection for the transmission of low frequency signals from the tunercontrol unit to the low frequency amplifyier of the amplifying unit anda electromagnetic coupling-type connection for the power supply of thetuner control unit.

According to another feature of the invention, the capacitive connectionfor the transmission of high frequency signals comprises two capacitorseach formed of two metallic plates disposed opposite to each other whenthe tuner control unit is inserted, located respectively in theamplifying unit and in the tuner control unit, preferably in the lowerface of the latter and separated by a plate of a dielectric material,such as ceramics, solid with the plate of the tuner control unit.

According to still another feature of the invention, the capacitiveconnection of the transmission of low frequency signals comprises atleast three capacitors, one for each stereophonic channel and one forthe return of the current, each comprising two metallic plates disposedopposite to each other when the tuner control unit is inserted, locatedrespectively in the amplifying unit and in the tuner control unit,preferably in the lower face of the latter and separated by a plate of adielectric material, such as ceramics, solid with the plate of the tunercontrol unit.

Preferably, the aforesaid dielectric material has a relativepermittivity between 500 to 2000.

According to still another feature of the invention, the electromagneticcoupling-type connection comprises two coupled windings locatedrespectively in the amplifying unit at the output of a directcurrent-alternating current converter and in the tuner control unit,preferably in the lower face thereof.

Advantageously, the system of the invention further comprises amechanical device released during the insertion of the tuner controlunit into the amplifying unit to press the rear part of the tunercontrol unit in order to perfectly ensure the aforesaid connections.

Moreover, the system of the invention comprises a knob for controllingthe ejection of the tuner control unit out of the housing of theamplifying unit.

Preferably, a secret code is memorized in the tuner control unit and iscompared to another secret code memorized in the amplifying unit and theputting into operation of the system is validated when a matchingbetween the two secret codes is ascertained, the comparison occuring forexample as soon as the amplifying unit is fed.

This latter feature is interesting as it completely dissuades any peoplefrom appropriating the amplifying unit solid with the dashboard of theautomotive vehicle since the same would be totally unusable in theabsence of the tuner control unit which normally should be associated toit.

BRIEF DESCRIPTION OF THE DRAWINGS

For fuller understanding of the invention, reference is made to thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a front view of a dashboard of an automotive vehiclecomprising the system according to the invention;

FIG. 2 is an enlarged perspective view in the direction of arrow II ofFIG. 1 of the system of the invention;

FIG. 3 is a perspective view of the tuner control unit according to afirst embodiment;

FIG. 4 is a partially broken way perspective view showing the mountingof the tuner control unit on a connector of the amplifying unitaccording to the invention;

FIG. 5 shows in the form of a block diagram the different electronicelements located respectively in the tuner control unit and in theamplifying unit of the system of the invention;

FIG. 6 is a top view in particular of the tuner control unit accordingto a second embodiment;

FIG. 7 is a view in the direction of arrow VII of FIG. 6;

FIG. 8 is a perspective view showing a mechanical device for maintainingthe tuner control unit in the housing of the amplifying unit; and

FIG. 9 shows in the form of a block diagrams the electrical elements orcircuits existing respectively in the tuner control unit and in theamplifying unit of the system of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 5, a radio receiver 1 is mounted on a stationarypart 2 of a vehicle constituted for example by the dashboard thereof.The radio receiver 1 comprises two separated parts, one part 3 forming aframe or amplifying unit solid in an inviolable manner, for example byfastening screws (not shown), with the rear face of the dashboard 2 andone part 4 for controlling the taking and the selection of AM or FMradio waves or tuner control unit with digital control keys 4a forexample of the touch contact type for searching for frequencies and forselecting the radio waves and with a display device 4b, in particularwith liquid crystals, for the searched for frequencies and stations. Thetuner control unit 4 is removably mounted in the supply unit 3 and is inthe shape of a right angled parallelepipedic flat casing having sizessimilar to the sizes of a payment card or a credit card and likely to beengaged in a central housing 5 having a shaped conjugate to that of theamplifying unit 3. In order to permit inserting the unit 4 inside thehousing 5, the dashboard 2 comprises a rectangular opening 6 locatedopposite the housing 5. The tuner control unit 4, when arrangedlongitudinally inside housing 5, leaves outside and therefore visibleabout one third of its surface so that the control keys 4a be accessibleand that the display device 4b in particular for the selected frequencyand the AM or FM wave range chosen, be also visible, the keys 4a and thedisplay device 4b being located on the upper face of unit 4. Thissurface portion of unit 4 which protrudes outwardly is carried by apedestal 7 made of hard rubber solid with the front face of thedashboard 2.

The unit 4 also comprises a certain number of metallic elements formingcontact studs 4c arranged longitudinally to the unit 4 and in parallelrelationship to each on the upper surface of unit 4 opposite to thecontrol keys 4a. The contact elements 4c are electrically connected tothe different electronic circuits arranged inside the casing of unit 4and which will be defined later. A connector 8, in the shape of aparallelepipedic bar, is fastened in the bottom part of the housing 5and comprises a groove 8a for receiving an end part of the casing ofunit 4. The connector 8 comprises several approximately curvilinearresilient parallel metallic strips 8b fastened to the upper face ofgroove 8a and ensuring electrical connections by pressing respectivelyon the contact elements 4c when the end part of the casing of unit 4 isinserted in groove 8a. Unit 4 is maintained in this inserted position bytwo retractable pusher-forming elements 9 and 10 solid with theamplifying unit 3 and located in aligned relationship on both sides ofunit 4, symmetrically to the longitudinal axis of the same. Moreprecisely, each push element 9, 10 comprises a tubular part 9a, 10asolid with the unit 3 and one end of which is obturated by a removableplug 9b, 10b accessible from the outside of unit 3 whereas the oppositeend comprises one ball 9c, 10c one part of which protrudes outwardlyfrom the corresponding tubular part in order to be inserted resilientlyin a corresponding housing 4d, 4e formed in a side face of the casing ofunit 4. The housings 4d and 4e both present a shape of an elongatednotch with a curveted bottom perpendicular to the upper plane face ofunit 4 and are arranged symmetrically to the longitudinal axis of unit4. It is of course possible to impart another shape to the housings 4dand 4e, for example the shape of a spherical cap. Each ball 9b, 10b ismaintained at the corresponding end of the tubular part 9, 10 by aresilient return element, such as a spring 9d, 10d coaxially mounted ina prestressed manner in the corresponding tubular part.

FIG. 5 shows the different electronic circuits present respectively inthe stationary part forming the amplifying unit 3 and in the removablepart constituted by the tuner control unit 4, the separation betweenthese two parts being symbolized by the dotted line L. On this line Lare symbolized the electrical connections C1 to C7 established when theresilient strips 8b are in contact respectively on the contact plugs 4conce the tuner control unit 4 inserted inside housing 5. Thus, theamplifying unit 3 comprises one low frequency amplifying circuit AMP ofwhich both outputs S are connected to loudspeakers (not shown) and whoseinputs are connected, through the medium of connections C6 and C7, tothe corresponding outputs of stereophonic pre-amplifying circuit PAMP1mounted in the tuner control unit 4. It is to be noted that theelectrical connection performed by connection C6 comprises in fact twoconnecting wires, each for one stereophonic channel, whereas theelectrical connection performed by connection C7 comprises at least onewire for the current return. The amplifying unit 3 comprises also theconnector (not shown) for connecting to the radio wave receiving antennasymbolized by ANT, and such that the antenna output is connected to theconnection C1 and the ground to the connection C2, which connections C1and C2 connect the antenna to the input of the high frequency circuitHFC of the tuner control unit 4. The connections L1 and L2 symbolize theelectric wires for connecting to an electrical supply device,constituted in the present case by the battery of the vehicle, andconnected respectively to connections C4 and C5 also connected to thesupply device SUP for the different circuits of the tuner control unit4. Lastly, the amplifying unit 3 comprises a device GEN for generating asecret code preferably established in the factory during the mounting ofthe radio receiver on the automotive vehicle. This generating device maybe of the type comprising a memory in which is memorized the secret codewhich is supplied at the output of the generating device for examplewhen the amplifying unit 3 is fed. Such a generating device need not bedescribed in detail as it is already known per se. The output of thegenerating device GEN is connected, through the medium of connection C3,to the input of a decoding circuit DEC of the tuner control unit 4capable of decoding the secret code memorized in the generating deviceGEN and, when the latter has been recognized, of transmitting a controlsignal authorizing the operation of a synthesizing device SYNT of thetuner control unit 4. The decoding device DEC comprises a memory whereina secret code is memorized before the tuner control unit 4 is deliveredto the user of the radio receiver, this code preferably being GEN of theamplifying unit 3. The decoding device DEC further comprises acomparator connected to the generating device GEN through connection C3and to the memory of decoding circuit DEC in order to compare the twosecret codes, and, in case of similarity of these codes, to deliver thecontrol output signal to the synthesizing circuit SYNT. The synthesizingcircuit SYNT is connected on the one hand to the control keys 4a and tothe display device 4b and on the other hand to the circuit HFC, whoseoutput is connected to an intermediate frequency circuit IFC. Theintermediate frequency signal at the output of the circuit IFC, afterbeing demodulated, is applied to the input of the pre-amplifying circuitPAMP1. The circuits HFC, IFC, SYNT, SUP and PAMP1 need not be describedin detail as they are conventional circuits.

Reference signs 11 and 12 designate two slots for introducingrespectively an analog or digital audio cassette and a laser audio disceach read in the amplifying unit 3, the reproducing means, which areknown per se, being not shown for the sake of clarity. The slots 11 and12 are located above the introduction opening 6 of the tuner controlunit 4.

The knobs (not shown) for controlling the adjusting of the volume of thesound and of the balance of the loudspeakers may be disposed near theintroduction opening 6 of the tuner control unit 4 on a front panel 13solid with the front face of the dashboard 2 and comprising variousindications concerning in particular the knobs for controlling theadjusting of the sound and of the balance of the loudspeakers. Ofcourse, the front panel 13 comprises rectangular passage or openingscommunicating respectively with the slots 11, 12 and the opening 6.

The circuits of the tuner control unit 4 may be mounted inside sameunder the form of plated circuit so that the unit 4 be as compact aspossible.

Thus, the tuner control unit 4 can be easily carried by a user inside apocket and he just has to introduce the unit 4 through the opening 6 inorder to insert it in the housing 5 and the connector 8 and to establishthe electrical connections defined above between unit 4 and amplifyingunit 3 so as to make the radio receiver operational after havingrecognized the secret codes memorized respectively in the amplifyingunit 3 and in unit 4. When he leaves momentarily his vehicle, the userwill remove the tuner control unit 4 by releasing if from the resilientholding elements 9 and 10 and putting it again in his pocket. Thereforeit will be impossible to steal the amplifying unit 3 withoutdeteriorating strongly the dashboard and the major element of the radioreceiver, namely the tuner control unit 4, which thus cannot be stolensince the user, owing to the small size and weight of this unit, similarto those of a credit card, will be able to leave it in his pocket.

The system according to the second embodiment shown in FIGS. 6 to 9differs from the first embodiment disclosed above only by the lateralintroduction of the tuner control unit 4, instead of being introducedlongitudinally as disclosed above, and by the electric coupling betweenunit 4 and amplifying unit 3.

According to this second embodiment, the control keys 4a and the displaydevice 4b are disposed longitudinally on the upper face of the controlunit 4 near the edge thereof so as to be visible once unit 4 insertedlaterally in its corresponding housing 5, the keys 4a being located onboth sides of the display device 4b.

The tuner control unit 4 comprises means cooperating respectively withother means of unit 3 for performing the electrical interconnectionbetween unit 4 and amplifying unit 3 once unit 4 is inserted in itscorresponding housing 5. The means of unit 4 are located side by side inan aligned manner near the longitudinal edge of unit 4 parallel to thatwhere the keys 4a and the display device 4b are arranged. These meansare arranged in the lower face of unit 4 and comprise first, from theleft to the right of FIG. 6 where unit 4 is being inserted in thedirection of arrow F1, three metallic plates having the shape ofcircular pastilles 14-16 each received and fastened, for example bygluing, on the bottom of a corresponding element 4f, 4g, 4h of unit 4and capable of cooperating respectively with three other metallic platesidentical to plates 14-16 having the shape of circular pastilles 17-19solid, for example by gluing, with the lower horizontal plane face 5a onthe bottom of housing 5 of the amplifying unit 3 so that the pairs ofplates 14, 17; 15, 18; 16, 19 each form a capacitive coupling for thetransmission of low frequency signals between pre-amplifyer PAMP1 ofunit 4 and low frequency amplifyer AMP of amplifying unit 3. A circularpastille P1 made from a dielectric material, such as ceramics, isreceived in each element 4f-4h and is fastened, for example by gluing,to a corresponding metallic plate 14, 15, 16, the pastilles P1 beinglocated respectively between plate 14, 17; 15, 18; 16, 19 in order toform dielectric capacitors. For example, each pastille P1 and thereforeeach circular plate 14-19 has a diameter of approximately 10 milimetersand each pastille P1 has a thickness of a few tenth of milimeter.Moreover, each pastille P1 has a relative permittivity comprised between500 and 2000 and is for example formed of ceramics of the type PXE whichhas been subjected to a depolarisation. The connection means comprisemoreover a winding 20 wound about a core 20a perpendicular to the lowerface of unit 4, the winding 20-core 20a assembly being received in ahousing in the shape of an element 4i formed in the lower face of unit4. The winding 20 cooperates with an identical winding 21 received in acorresponding element of face 5a so that in the inserted position ofplate 4, the windings 20 and 21 are located in opposite relationship oneabove the other for ensuring an electromagnetic coupling necessary tothe electric power supply of the tuner control unit 4. The winding 21 iswound about a core 21a perpendicular to face 5a. Lastly, the connectionmeans comprise two metallic plates having the shape of circular pastille22, 23 each received on the bottom of a housing forming a correspondingelement 4j and 4k formed in the lower face of unit 4 and fastened bygluing. The two plates 22 and 23 cooperate respectively with two othermetallic circular plates with identical dimensions 24 and 25 fastenedfor example by gluing, on the face 5a so that in the inserted positionof plate 4 they are in opposite relationship one above the other forensuring a capacitive coupling for the transmission of high frequencysignals between the output of antenna ANT and high frequency circuit HFCof unit 4 and another capacitive coupling ensuring the there and backconnection of the necessary current. It is further to be noted that eachof the two capacitors formed respectively by plates 14, 17 and 15, 16corresponds to one stereophonic channel whereas the capacitor formed byplates 16, 19 ensures the necessary return of the current. Finally, twopastilles P2 made from a dielectric material, such as ceramics, arefastened, for example by gluing, respectively to plates 22 and 23 andform two dielectric capacitors in the inserted position of unit 4.

Referring to FIG. 9, where the dotted line L shows the separationbetween the stationary part of amplifying unit 3 and the removable partconstituted by the tuner control unit 4, the different types of couplingdefined above are represented by their respective symbols located online L. This Figure shows the presence of a direct current-alternatingcurrent converting circuit CV, constituted for example by a choppercircuit, and converting the direct current of supply from the battery ofthe vehicle into an alternating circuit for transmitting the electricpower of supply to a rectifying circuit RD through the medium ofwindings 20 and 21, the output of the rectifying supplying the variouscircuits of unit 4 which are otherwise identical to those shown in FIG.5 with one difference in that the circuit DEC for decoding the secretcode is connected at the output of the rectifying circuit RD so as toreceive the secret code from amplifying unit 3 transmitted to therectifying circuit RD through the medium of the converting circuit CV towhich is connected the code generator GEN, which secret code istransmitted to the decoding circuit DEC for example when the supply unit3 is fed. Reference PAMP2 designates a pre-amplifyer for antenna ANTconnected to the high frequency circuit HFC through the medium ofcapacitors 22, 24 and 23, 25.

Of course, the plates of the different capacitors and the windings shownin FIG. 6 are electrically connected to the different circuits ofamplifying unit 3 and of unit 4 in the manner shown in FIG. 9. It isfurther to be noted that the capacitors formed for the transmission oflow frequency signals in the inserted position of unit 4 in theamplifying unit 3 also permit eliminating intermediate frequencies.

FIG. 8 shows a mechanical device permitting pressing the rear part oftuner control unit 4 in order to maintain it in position and toperfectly ensure the capacitive and electromagnetic couplings describedabove once unit 4 in position of use inside its corresponding housing 5.The bottom of the latter terminates by a cavity 5b whose upper wallpresents a cross-section substantially in the shape of an arc of acircle and adapted to permit the tilting about its longitudinal axisX-X' of a heel-forming part 26, forming part of the above-mentionedmechanical device, and provoked by the introduction of unit 4 at thebottom 5b of its housing 5. The heel-forming part 26 is shown in dottedline in inactive position inclined at about 45° with respect to thehorizontal, and is maintained in this position by a return spring 27fastened at one of its ends to an elongated lower semi-cylindrical partforming a stop 26a of the heel-forming part 25 and at its other oppositeend to a stationary point of the amplifying unit 3. The semi-cylindricalpart 26a is connected to an elongated parallelepipedic part 26bperpendicular to the part 26a and of which one lower plane phase 26b1rests on the upper face of the end part of the control unit 4 in theactive position of the heel-forming part 26.

A mechanical ejection device is provided also for ejecting the tunercontrol unit 4 out of its housing 5. This device comprises one lever arm28 having one of its ends solids with the extreme face of theheel-forming part 26 opposite to that where one of the ends of thereturn spring 27 is fastened and its other opposite end connected in anhinged manner to an element 29 forming a push button for ejecting thecard 4. The element 29 is slidebly mounted through the front wall of thedashboard 2 and protrudes outwardly from the same in order to beaccessible.

Before introducing the tuner control unit 4 into its housing 5, theheel-forming part 26 is in the awaiting position shown in dotted lines.When the unit 4 is introduced into housing 5, the rear end of the samerests against the stop-forming part 26a so as to tilt the heel-formingpart 26 clockwise in cavity 5b about its axis X-X' until the plane face26b1 of part 26b rests on plate 4, maintaining the latter correctly inposition and ensuring perfectly the capacitive and electromagneticcouplings. The fixing point of the spring to the extreme face of thestop-forming part 26a move on an approximately circular trajectory fromthe position shown in dotted lines to the position shown in continuousline. The heel-forming part 26 is blocked in active position by thesemi-cylindrical part 26a abutting against the rear extreme face of unit4 and also by the lever arm 26, the spring 27 having a very weak returnforce. The user who wants to recover the tuner control unit 4 pressesthe push element 29 towards the left with respect to FIG. 8 so as topivote the lever arm 28 in a direction corresponding to the tilting ofthe heel-forming part 26 towards its awaiting position in dotted lines.During this tilting of the heel-forming part 26 the semi-cylindricalpart 26a pushes back the unit 4 towards the right in the direction ofarrow F2 in order to partly eject it from its housing 5.

Advantageously, a stroke end contact (not shown) is associated with theheel-forming part 26 to permit supplying the amplifying unit 3-unit 4assembly with electrical power when the latter is in the insertedposition as shown in FIG. 8.

Various modifications can be made in the two above describedembodiments. Thus, due to the fact that unit 4 according to the secondembodiment is laterally inserted into its housing 5, it is possible toinsert a maximum number of keys higher than the eight keys already shownfor ensuring other functions such as memory functions permittingmemorizing one or several chosen stations. Moreover, the secret codememorized on the removable unit 4 can be magnetically recorded likecredit cards and read by a magnetic reading device arranged in theamplifying unit 3. Thus, this confidential code will be recorded on themagnetic card delivered with the material at the time of the purchase,in order to be able to introduce the initial code on a second radio cardin case of loss. The ejection device described in the second embodimentcan be used also for ejecting the unit 4 of the first embodiment.Finally, a portable casing of the size of a conventional packet ofcigarettes, comprising an electric power supply system (electric batteryor cell) and amplifiers connected to a small foldable headset willenable the user of the radio card 4 to complete the hearing of thestation on which it is connected, outside his vehicle.

I claim:
 1. A radio receiving system used in an automotive vehicle,comprising: an amplifying unit for amplifying audio signals, fixed, inan inviolable manner, to a rear face of a dashboard of the vehicle and atuner control unit for controlling the acquisition and the selection ofradio waves, said tuner control unit being removably secured to saidamplifying unit, the system further including means for electricallyconnecting said tuner control unit to said amplifying unit, said tunercontrol unit including a casing being in the shape of a flatparallelepiped and being approximately equal in size to a credit card,said amplifying unit including a housing having an opening that iscomplementary in shape to the shape of the tuner control unit, saidtuner control unit being insertable through a rectangular opening in thedashboard and into said amplifying unit housing opening to electricallyconnect said tuner control unit to said amplifying unit, said tunercontrol unit includes a part which carries control elements forsearching for particular radio wave frequencies and for selecting radiowaves and a device for displaying the status of the radio system, whensaid tuner control unit is inserted into said amplifying unit said partof said tuner control unit extends from said amplifying unit so as to bevisibly external thereto, said electrical connecting means comprisingfirst and second connecting elements, said first connecting elementsbeing provided directly on the casing of the tuner control unit side byside at the rearwards part of the casing opposite to the externalvisible part, said second connecting elements being provided within theamplifying unit housing such that said second connecting elements facessaid first connecting elements when said tuner control unit is insertedin said amplifying unit housing opening to transmit signals between saidtuner control and amplifying units, said first and second connectingelements form a capacitive coupling-type connection for transmittinghigh frequency signals coming from an antenna to high frequency circuitsof the tuner control unit, a capacitive coupling-type connection fortransmitting low frequency signals from the tuner control unit to a lowfrequency amplifier of the amplifying unit, an electromagneticcoupling-type connection for the power supply of the tuner control unit,said capacitive-type connection for transmitting high frequency signalscomprises two capacitors each formed of two metal plates disposedopposite to each other when the tuner control unit is positioned insidesaid amplifying unit housing, one of said capacitors being positioned insaid amplifying unit and the other of said capacitors being positionedin said tuner control unit, said capacitors being separated by a platemade from a dielectric material and fixed to the tuner control unit. 2.The system according to claim 1, wherein the display device is of theliquid crystal type and the control elements are keys of the touchcontact type.
 3. The system according to claim 1, wherein the amplifyingunit further comprises two housings for receiving respectively oneanalog or digital cassette and one laser reading disc.
 4. The systemaccording to claim 1, wherein said electrical connecting means comprisesplugging means having one connector at the bottom of the casingincluding a certain number of resilient metallic contact strips formingsaid second connecting elements and, located on the upper face of thetuner control unit rearwards thereof, a certain number of contact plugsforming said first connecting elements cooperating respectively with themetallic strips.
 5. The system according to claim 1, wherein the visiblepart of the tuner control unit rests on a pedestal made of hard rubberand fixed to the front face of the stationary part of the vehicle. 6.The system according to claim 1, wherein a secret code is memorized inthe tuner control unit and is compared to another secret code memorizedin the amplifying unit and wherein the putting in operation of thesystem is validated in case of matching of the two secret codes, thecomparison occurring as soon as the amplifying unit is supplied.
 7. Aradio receiving system used in an automotive vehicle, comprising: anamplifying unit for amplifying audio signals, fixed, in an inviolablemanner, to a rear face of a dashboard of the vehicle and a tuner controlunit for controlling the acquisition and the selection of radio waves,said tuner control unit being removably secured to said amplifying unit,the system further including means for electrically connecting saidtuner control unit to said amplifying unit, said tuner control unitincluding a casing being in the shape of a flat parallelepiped and beingapproximately equal in size to a credit card, said amplifying unitincluding a housing having an opening that is complementary in shape tothe shape of the tuner control unit, said tuner control unit beinginsertable through a rectangular opening in the dashboard and into saidamplifying unit housing opening to electrically connect said tunercontrol unit to said amplifying unit, said tuner control unit includes apart which carries control elements for searching for particular radiowave frequencies and for selecting radio waves and a device fordisplaying the status of the radio system, when said tuner control unitis inserted into said amplifying unit said part of said tuner controlunit extends from said amplifying unit so as to be visibly externalthereto, said electrical connecting means comprising first and secondconnecting elements, said first connecting elements being provideddirectly on the casing of the tuner control unit side by side at therearwards part of the casing opposite to the external visible part, saidsecond connecting elements being provided within the amplifying unithousing such that said second connecting elements faces said firstconnecting elements when said tuner control unit is inserted in saidamplifying unit housing opening to transmit signals between said tunercontrol and amplifying units, said first and second connecting elementsform a capacitive coupling-type connection for transmitting highfrequency signals coming from an antenna to high frequency circuits ofthe tuner control unit; a capacitive coupling-type connection fortransmitting low frequency signals from the tuner control unit to a lowfrequency amplifier of the amplifying unit; and an electromagneticcoupling-type connection for the power supply of the tuner control unit,said capacitive-type connection for transmitting high frequency signalscomprises three capacitors for each stereophonic channel and one forreturn of current and each comprising two metallic plates disposedopposite to each other in the inserted position of the control unitinside said amplifying unit housing, located respectively in theamplifying unit and in the tuner control unit and separated by a platemade of a dielectric material and fixed to the plate of the tunercontrol unit.
 8. The system according to claim 7, wherein saidcapacitive-type connection for transmitting low frequency signalscomprises at least three capacitors for each stereophonic channel andone for return of current and each comprising two metallic platesdisposed opposite to each other in the inserted position of the tunercontrol unit inside housing, located respectively in the amplifying unitand in the tuner control unit, and separated by a plate made of adielectric material with fixed to the plate of the tuner control unit.9. The system according to claim 8, wherein said dielectric material hasa relative permittivity of about 500 to about
 2000. 10. The systemaccording to claim 7, further comprising a mechanical device released atthe time of the insertion of the tuner control unit into the housing forpressing the rear part of the tuner control unit in order to perfectlyensure said connections.
 11. The system according to claim 7, furthercomprising an element for controlling the ejection of the tuner controlunit out of the housing.
 12. A radio receiving system used in anautomotive vehicle, comprising: an amplifying unit for amplifying audiosignals, fixed, in an inviolable manner, to a rear face of a dashboardof the vehicle and a tuner control unit for controlling the acquisitionand the selection of radio waves, said tuner control unit beingremovably secured to said amplifying unit, the system further includingmeans for electrically connecting said tuner control unit to saidamplifying unit, said tuner control unit including a casing being in theshape of a flat parallelepiped and being approximately equal in size toa credit card, said amplifying unit including a housing having anopening that is complementary in shape to the shape of the tuner controlunit, said tuner control unit being insertable through a rectangularopening in the dashboard and into said amplifying unit housing openingto electrically connect said tuner control unit to said amplifying unit,said tuner control unit includes a part which carries control elementsfor searching for particular radio wave frequencies and for selectingradio waves and a device for displaying the status of the radio system,when said tuner control unit is inserted into said amplifying unit saidpart of said tuner control unit extends from said amplifying unit so asto be visibly external thereto, said electrical connecting meanscomprising first and second connecting elements, said first connectingelements being provided directly on the casing of the tuner control unitside by side at the rearwards part of the casing opposite to theexternal visible part, said second connecting elements being providedwithin the amplifying unit housing such that said second connectingelements faces said first connecting elements when said tuner controlunit is inserted in said amplifying unit housing opening to transmitsignals between said tuner control and amplifying units, said first andsecond connecting elements form a capacitive coupling-type connectionfor transmitting high frequency signals coming from an antenna to highfrequency circuits of the tuner control unit; a capacitive coupling-typeconnection for transmitting low frequency signals from the tuner controlunit to a low frequency amplifier of the amplifying unit; and anelectromagnetic coupling-type connection for the power supply of thetuner control unit, said electromagnetic coupling-type connectingcomprising two coupled windings located respectively in the amplifyingunit at an output of a direct current-alternating current convertor andin the tuner control unit.